Flat bed type image scanners have been widely used to "read" images formed on sheet-like media, such as paper or film. The flat bed type image scanners usually comprise a box-like machine body on which a light-transmitting image window is formed. Paper or film on which image to be scanned is printed is placed on the image window. For reading images on non-transparent media, such as paper, a paper cover is provided to cover the image window with the paper to be scanned disposed therebetween. A line light source which is disposed inside the box-like machine body to project light to the paper to be scanned moves inside the machine body from one end to the other end to allow the paper to be fully scanned by the light. Reflection of the scanning light provides information of the image printed on the paper to the scanner. The scanner receives the reflected light and further processes it to provide desired signal.
For scanning a substantially transparent medium, such as a film, back lighting provided by a back lighting module disposed on the film is a must for the scanning operation. The back lighting module which is displaced on the position of the paper cover emits light from the back side of the film and the light so emitted transmits through the film and is then projected toward an optical reading module inside the image scanner.
The light source for a conventional image scanner, for scanning both transparent and non-transparent media is complicated and sophisticated in structure and design and thus cost in manufacturing and maintenance.
It is therefore desirable to provide a transparency adaptor for use in a flat bed type image scanner to facilitate the reading of images printed on light-transmittable medium.